Difficulties have been encountered in making cushioned bags of tear resistant material since tear resistant synthetic non-woven fibrous sheet material, such as Tyvek (manufactured by E. I. Dupont de Nemours and Company), is unable to be heat sealed to itself by known methods. Consequently, bags having Tyvek as an outside layer have heretofore been sealed adhesively.
A known shipping bag using Tyvek is described in Bambara, U.S. Pat. No. 3,948,436. The bag uses Tyvek as one of the middle layers, with a layer of polyethylene film adhesively bonded on either side of the Tyvek. Other patents showing cushioned shipping bags having a kraft outer layer and a foam lining, and methods for making such bags, include Bambara, U.S. Pat. No. 4,011,398 and 4,087,002, and Studen, U.S. Pat. No. 3,256,527. The Studen patent shows heat sealing of a seam by passing the material between heated jaws, but Studen shows the jaws having plane surfaces for contacting the layers. These plane surfaces are curved away from the seamed edge on the side toward the interior of the bag, and the jaws of Studen produce a flat, fin-type seam of two layers of foam laminated together, optionally having an outer layer of paper.